CANBERRA
(Reuters) - The summer ice melt in parts of Antarctica is at its
highest level in 1,000 years, Australian and British researchers
reported on Monday, adding new evidence of the impact of global
warming on sensitive Antarctic glaciers and ice shelves.

Researchers
from the Australian National University and the British Antarctic
Survey found data taken from an ice core also shows the summer ice
melt has been 10 times more intense over the past 50 years compared
with 600 years ago.

"It's
definitely evidence that the climate and the environment is changing
in this part of Antarctica," lead researcher Nerilie Abram said.

Abram
and her team drilled a 364-metre (400-yard) deep ice core on James
Ross Island, near the northern tip of the Antarctic Peninsula, to
measure historical temperatures and compare them with summer ice melt
levels in the area.

They
found that, while the temperatures have gradually increased by 1.6
degrees Celsius (2.9 degrees Fahrenheit) over 600 years, the rate of
ice melting has been most intense over the past 50 years.

That
shows the ice melt can increase dramatically in climate terms once
temperatures hit a tipping point.

"Once
your climate is at that level where it is starting to go above zero
degrees, the amount of melt that will happen is very sensitive to any
further increase in temperature you may have," Abram said.

Robert
Mulvaney, from the British Antarctic Survey, said the stronger ice
melts are likely responsible for faster glacier ice loss and some of
the dramatic collapses from the Antarctic ice shelf over the past 50
years.